1. Field of the Invention
The present invention relates to an optical disk and optical disk drive, and more particularly, to a high-definition optical disk and a high-definition optical disk drive, which record/reproduce data through use of grooves and lands.
2. Description of the Related Art
There has hitherto been known an optical disk which achieves a high recording definition (or density) by means of recording data not only on a groove, but on both a groove and a land. When data are recorded on both the groove and the land in the manner as mentioned above, an address must be accurately detected from the groove and the land, respectively. In DVD-RAM, a special signal is inserted on a per-sector basis so as to be temporally independent of data recording according to a scheme called CAPA (Complementary Allocated Pit Address), and an address is detected by means of reproducing this special signal. Specifically, an address area (header section) which is independent of a data area is provided at the head of each sector. A plurality of CAPA signals are inserted into the header section while being offset right and left with respect to the groove or land in the data area. CAPA signals detected when data are recorded/reproduced on or from the groove differ from those detected when data are recorded/reproduced on or from the land. By utilization of this phenomenon, detection of an address from the groove and an address from the land is performed.
However, the optical disk has the address sections which are temporally independent of the data sections, and, therefore, there arises a problem of the data capacity of the optical disk being reduced correspondingly. Further, the groove and the CAPA signals are not arranged in a straight line, and hence there also arises a problem of manufacture of an optical disk encountering comparative difficulty. Moreover, there still exists a problem of a servo system employed for recording/reproducing data on/from the data section differing from that employed for recording/reproducing data on/from the header section, or a problem of the data section differing from the header section in terms of optimum points of parameters, such as servo parameters.
For these reasons, there has already been put forward a technique for determining the address of the land (hereinafter sometimes be called a “land address”) as well as the address of the groove (hereinafter sometimes be called a “groove address”) through use of wobbles to be used for storing the groove address.
When the groove is subjected to in-phase wobbling at a phase of 0°, 0 is recorded. When the groove is subjected to in-phase wobbling at a phase of 180°, 1 is recorded. Thus, address information is embedded. However, even when two adjacent grooves are subjected to in-phase wobbling, a land sandwiched between the two grooves is not necessarily subjected to in-phase wobbling, thereby failing to determine an address. In light of this problem, a technique for preparing two addresses and determining the land address through use of anyone of them is described in, e.g., Japanese Patent Laid-Open Publication No. Hei 10-312541.
FIG. 21 shows an address format described in the conventional technique.
The address includes an area address and a track address (i.e., a track number), and the area addresses of the respective segments arranged in the same direction are equal to each other. FIG. 21 shows only track addresses. Reference symbols G1, G2, G3, . . . denote grooves; and L1, L2, L3, . . . denote lands. Lower track numbers are located in an inner radius of the disk, and the track number increases from the inner radius to the outer radius. A track number assigned to G1 is n+1; a track number assigned to G2 is n+2; a track number assigned to L1 is n+1; and a track number assigned to L2 is n+2. As shown in FIG. 22, wobbles are formed in each of the grooves; 0 is recorded through use of the in-phase wobbles of 0°, and 1 is recorded through use of in-phase wobbles of 180°.
When attention is directed toward G1, L1, and G2, the track numbers assigned to G1, G2 originally differ from each other. Accordingly, the wobbles formed in G1 and those formed in G2 become out of phase with each other. In L1 sandwiched between G1 and G2, the wobbles of G1 and the wobbles of G2 are 180° out of phase with each other, and hence L1 becomes opposite in phase and cannot be detected. For this reason, in relation to Address 1, an identical track number is assigned to G1 and G2, thereby bringing the wobbles of L1 sandwiched therebetween in phase and enabling determination of a track number n+1. In Address 2, the original track number n+1 is assigned to G1, and the original track number n+2 is assigned to G2. Therefore, the address of L1 sandwiched between G1 and G2 cannot be detected, and hence NG is assigned to L1.
When attention is directed toward G2, L2, and G3, the track numbers assigned to G2, G3 originally differ from each other. Accordingly, the wobbles formed in G2 and those formed in G3 become out of phase with each other. In L2 sandwiched between G2 and G3, the wobbles of G2 and the wobbles of G3 are 180° out of phase with each other, and hence L1 becomes opposite in phase and cannot be detected. For this reason, in relation to Address 2, an identical track number is assigned to G2 and G3, thereby bringing the wobbles of L2 sandwiched therebetween in phase and enabling determination of a track number n+2. In this case, in Address 1, the address of L2 cannot be detected, and hence NG is assigned to L2.
When address data are recorded on the disk in the form of wobbles, recording is performed by means of converting binary data into a gray code. Here, the gray code is for setting an inter-code distance between two adjacent sets of binary data; that is, the number of inverted bits.
FIG. 23 shows a gray code converter 2 for converting binary data into a gray code. FIG. 24 shows a relationship between addresses and gray codes. The gray code converter 2 comprises a plurality of EX-OR (exclusive-OR) gates 1. For instance, when the address is made up of eight bits, the least significant bit LSB and the next lower bit are subjected to EX-OR operation, thereby determining the least significant bit LSB of the gray code. Similarly, adjacent bits in the address are subjected to EX-OR operation and converted into a gray code. The most significant bit MSB of the address is maintained intact and converted into a gray code. In the EX-OR operation, 0 is output when two inputs are identical with each other, and 1 is output when the two inputs differ from each other. Therefore, for instance, when binary data pertaining to the address are 00000000, the gray code will assume 00000000. When the binary data are 00000001, the gray code assumes 00000001. When binary data are 00000010, the gray code assumes 00000011. As can be seen from FIG. 24, the inter-code distance of a gray code existing between two consecutive addresses always assumes a value of 1.
As mentioned above, the land address and the groove address have hitherto been detected through use of the two addresses; that is, Address 1 and Address 2. However, forming two addresses in a disk beforehand is redundant, and a data recording density of the disk is decreased correspondingly. The conventional technique employs only one of the addresses. Even if the two addresses are used, effective utilization of a redundant address is not sought.